*{
    margin: 0px;
    padding: 0px;
    box-sizing: border-box;
}
ul,ol,dl{
    list-style: none;
}
a{
    text-decoration: none;
}
footer>div{
    width: 100%;
}
img{
    width: 100%;
    height: 288px;
}
nav{
    width: 80%;
    margin: 0 auto;
}
.nav_ul1{
    display: flex;
    justify-content: space-between;
    height: 150px;
    line-height: 150px;
}
.nav_ul1>li>img{
    width: 18rem;
    margin-top: -70px;
    position: relative;
    z-index: -1;
}
.nav_ul1>li{
    position: relative;
}
.posi{
    position: absolute;
    top: 50px;
    display: none;
    height: 20px;
}
.posi>a{
    color: #333;
}
.posi>a:hover{
    color:#2b86ed;
}
.nav_ul1>li:nth-child(6):hover>.posi{
    display: block;
}
.nav_ul1>li>a{
    color: #333;
}
.nav_ul1>li:hover>a{
    color:#2b86ed;
}

.b>img{
        width: 100%;
        height: 100%;
        margin-bottom: 5rem;
    }
.flex{
    display: flex;
}
.just{
    justify-content: space-between;
}

